Track the bug. The bug will be the place where your submission is discussed, edits are suggested, etc.

If you are suggestion or request isn't at that concrete a level, feel free to add some discussion text to the [Talk:User_Interface_Guidelines] page.

Add your content

Minor Edits:

If you are making minor edits (e.g. fixing typos or small inaccuracies) then do so in place.

Make a comment in the bug with respect to the changes you've made.

Major Edits:

If you are creating a new section, or making extensive edits to an existing one, make a new wiki page linked to Talk:User_Interface_Guidelines and add your content. If you are editing an existing section, make a copy of it in a new page and edit from there. This allows you to work in a sandbox.

Put a comment at the top of the existing page, "*** UNDER CONSTRUCTION bug #123 *** with the your bug number. This is a safeguard to ensure two people don't start making major edits to the same section and potentially either duplicate or lose work.

Have things reviewed

Change the status of the bug to resolved with resolution fixed. This will trigger review.

Wait a while. If there is violent objection someone will reopen the bug. Discussion can happen on the bug thread or UI Best Practices Working Group mailing list. Issues can also be brought up at one of the meetings.

Merge your changes into the drafts

If after one week nobody has raised any objections to the changes, move your content from the sandbox to the draft pages here: UI Best Practices v3.x